WASHINGTON — It was a first for Washington, a black-tie AIDS benefit selling out 1,000 tickets at $125 each. Never had there been such a large show of strength for the AIDS issue in this image-conscious capital.

"We're just very elated," said Vic Basile, executive director of the Human Rights Campaign Fund, the gay and lesbian political action committee that sponsored the dinner last week. AIDS, acquired immune deficiency syndrome, is a fatal disease striking primarily homosexual men and intravenous drug users in this country.

"Little did we dream that tonight, in this room in Washington, there would be 1,000 people," said Vivian Shapiro, co-chair of the fund. "Last year there were only 250."

The lavish dinner at the Sheraton Washington and an earlier reception raised $130,000 for the newly formed AIDS Campaign Trust, the only organization whose sole function is to donate money to the campaigns of political candidates who favor increased federal funding for AIDS research and treatment.

The trust announced the first 12 candidates who would receive $1,000 each for their 1986 campaigns, and they include California Reps. Henry A. Waxman (D-Los Angeles), who gave the dinner's keynote speech, Edward R. Roybal (D-Los Angeles), Tony Coelho (D-Merced) and Barbara Boxer (D-Greenbrae), along with Sen. Alan Cranston (D-Calif.).

Sex therapist Ruth Westheimer received a standing ovation before she took the microphone as emcee. Westheimer has fascinated millions with her radio and television appearances, giving advice on what she enthusiastically labels "good sex."

"I can't talk about good sex on an empty stomach," Westheimer, 57, said. "So let's have dinner and let the evening begin."

Although it was a tragic cause that brought the predominantly male group together, the mood was upbeat. After lighting white candles at each table to mourn those who suffer from AIDS, the evening went on to include lively entertainment and discoing after midnight at Tracks, a Washington nightspot.

The affair was billed as a salute to Broadway composer Jerry Herman, and he saluted back by singing his song, "I Am What I Am" from "La Cage aux Folles." The Gay Men's Chorus also performed.

The party was attended almost entirely by members of Washington's gay community. Among the recognizable figures in the crowd were Rep. Ted Weiss (D-N.Y.), Larry Kramer, author of "The Normal Heart," a play about AIDS, and Robin Weir, Nancy Reagan's Washington hairdresser.

In his keynote speech, Waxman compared the spread of AIDS to the Vietnam War, predicting it will kill many thousands and ultimately divide the country.

"If the epidemic continues at this rate," Waxman said, "by the end of the Reagan presidency nearly twice as many Americans will have died of AIDS than died in Vietnam. The costs in medical care alone are estimated to be $8 billion, with untold billions more in lost productivity.

"The losses of the Vietnam War deeply changed this country and the world. I hope to be proven wrong, but I believe that in the next few years AIDS will deeply change this country as well."

At the $125-per-person reception before the dinner, Westheimer said that she had "no patience and no time" for those who claim that AIDS is the result of perversion and promiscuity, promoted publicly by people like herself.

"If anybody is offended by my radio program, they should not listen to it," said Westheimer. "Children will hear talk about sex; you can't prevent it. So I say, let them hear it from me rather than the gutter. I always tell them to wait to have sex, not to succumb to pressure."